According to related-art technology, a polycarbosilane is generally cured by (i) forming Si—O—Si bonds by firing in an oxidizing atmosphere (U.S. Pat. No. 5,602,060 and US-A-2003/0017635), or (ii) forming Si—Si bonds by coupling Si—H bonds and then forming Si—C—Si bonds via a rearrangement reaction (US-A-2003/0017635).
However, when the method (i) is utilized for a semiconductor integrated circuit production process, metal wires formed on a substrate may be oxidized so that the wiring resistance may increase. According to the method (ii), a curing reaction proceeds to a larger extent as the Si—H bond content of the polymer increases. However, a dehydrogenation coupling reaction gradually occurs during storage due to the high Si—H bond content, whereby the polymer may deteriorate.
As a polycarbosilane which solves the above problems, can be cured under reduced pressure or an inert gas atmosphere, and is chemically stable, (i) a polycarbosilane which has a crosslinkable side chain other than the Si—H bond or is readily cured by heating or the like due to introduction of a moderately crosslinked structure before crosslinking, or (ii) a polycarbosilane which further has an appropriate number of Si—H bond side chains which enable a dehydrogenation coupling reaction is preferable. In the case of a polycarbosilane which can be cured only by the mechanism described in (i), the number of crosslinked sites in the polymer increases. As a result, thermal stability and mechanical strength may decrease when the crosslinked site is an organic group. When the crosslinked site has a siloxane structure, resistance to processing such as etching and plasma processing may decrease in semiconductor integrated circuit applications.
US-A-2003/0017635 discloses a method which applies a polycarbosilane which does not have an Si—O bond to a silicon wafer and heats the polycarbosilane in air to form an Si—O—Si bond via oxidation, and JP-A-2003-142477 and JP-T-8-510292 disclose polymers obtained by modifying a polycarbosilane having an Si—H bond in an organic solvent using alkali and water. However, a polycarbosilane which does not affect other materials such as wires when applied to a semiconductor integrated circuit production process and exhibits excellent storage stability has not yet been obtained.